Thor's Helmet
NGC 2359 · Emission nebula in Canis Major
- Magnitude
- 11.5
- Size
- 8′
- Effective surface brightness
- 22.9 mag/arcsec²
- Best months
- Dec, Jan, Feb
- Declination
- -13°
- Filter
- Dual-band recommended
A Wolf-Rayet bubble with wings, strong in OIII. Small and faint; dual-band is essential and a bigger scope helps.
Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
How long with each smart telescope
| Telescope | In frame | Bortle 3 (rural) | Bortle 5 (suburban) | Bortle 7 (urban edge) |
|---|---|---|---|---|
| ZWO Seestar S5010 s subs, dual-band | 19% | 4 h 16 min1,535 subs | 5 h 04 min1,826 subs | 8 h 37 min3,102 subs |
| ZWO Seestar S50 Pro10 s subs, dual-band | 10% | 4 h 53 min1,756 subs | 5 h 45 min2,072 subs | 9 h 35 min3,451 subs |
| ZWO Seestar S3010 s subs, dual-band | 11% | 5 h 23 min1,936 subs | 6 h 11 min2,227 subs | 9 h 44 min3,502 subs |
| ZWO Seestar S30 Pro10 s subs, dual-band | 6% | 5 h 20 min1,918 subs | 6 h 15 min2,249 subs | 10 h3,700 subs |
| DwarfLab DWARF 315 s subs, dual-band | 8% | 4 h 33 min1,092 subs | 5 h 48 min1,393 subs | 11 h2,706 subs |
| DwarfLab DWARF mini15 s subs, dual-band | 11% | 4 h 10 min999 subs | 4 h 58 min1,194 subs | 8 h 31 min2,044 subs |
| DwarfLab Draco30 s subs, dual-band | 11% | 3 h 16 min393 subs | 3 h 57 min474 subs | 6 h 54 min828 subs |
| DwarfLab DWARF II15 s subs | 7% | 17 h4,153 subs | 25 h5,918 subs | 57 h13,631 subs |
| Vaonis Vespera II10 s subs | 9% | 3 h 43 min1,340 subs | 6 h 22 min2,293 subs | 18 h6,458 subs |
| Vaonis Vespera Pro10 s subs | 8% | 9 h 18 min3,348 subs | 15 h5,352 subs | 39 h14,109 subs |
| Vaonis Vespera 310 s subs | 9% | 3 h 31 min1,267 subs | 6 h 04 min2,182 subs | 17 h6,182 subs |
| Vaonis Vespera Pro 210 s subs | 8% | 8 h 45 min3,153 subs | 14 h5,077 subs | 37 h13,487 subs |
| Unistellar eQuinox 24 s subs | 23% | 5 h 23 min4,852 subs | 7 h 02 min6,337 subs | 14 h12,826 subs |
| Unistellar Odyssey4 s subs | 24% | 29 h26,368 subs | 35 h31,770 subs | 62 h55,383 subs |
| Celestron Origin10 s subs | 16% | 51 min306 subs | 1 h 36 min576 subs | 4 h 53 min1,758 subs |
| Celestron Origin Mark II10 s subs | 18% | 1 h 02 min371 subs | 2 h 07 min760 subs | 6 h 50 min2,461 subs |
Imaging the emission nebula
Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.
Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.
Per-telescope pages
- How long to image the Thor's Helmet with the ZWO Seestar S50
- How long to image the Thor's Helmet with the ZWO Seestar S50 Pro
- How long to image the Thor's Helmet with the ZWO Seestar S30
- How long to image the Thor's Helmet with the ZWO Seestar S30 Pro
- How long to image the Thor's Helmet with the DwarfLab DWARF 3
- How long to image the Thor's Helmet with the DwarfLab DWARF mini
- How long to image the Thor's Helmet with the DwarfLab Draco
- How long to image the Thor's Helmet with the DwarfLab DWARF II
- How long to image the Thor's Helmet with the Vaonis Vespera II
- How long to image the Thor's Helmet with the Vaonis Vespera Pro
- How long to image the Thor's Helmet with the Vaonis Vespera 3
- How long to image the Thor's Helmet with the Vaonis Vespera Pro 2
- How long to image the Thor's Helmet with the Unistellar eQuinox 2
- How long to image the Thor's Helmet with the Unistellar Odyssey
- How long to image the Thor's Helmet with the Celestron Origin
- How long to image the Thor's Helmet with the Celestron Origin Mark II